Sensor Driver? Sensor Fusion?

by Bryon Moyer

Not long ago, coincident with Sensors Expo, Freescale announced their new Intelligent Sensing Framework, or ISF. From the initial descriptions I saw, I was frankly a bit confused as to how this is different from a driver and from other sensor fusion solutions. A conversation with Freescale’s Jim McGlasson helped add some color to what’s going on.

As a starting point, we can remind ourselves that a driver is a piece of code running on a host (or AP or whatever) that lets that host access a resource. In the case of a sensor, the driver can poke and prod at the sensor to configure it or retrieve data. The API and other hooks are typically defined by the operating system; this lets the sensor behave in a way that the OS is expecting, and it abstracts the sensor details from the upper layers.

While the ISF is described as providing sensor abstraction, it does not behave like a driver. By definition, the ISF isn’t intended to run on the host: it runs on the sensor.

“How,” you ask, “can code run on a sensor??” The short answer is, “It can’t.” Unless there’s a microcontroller in there. Which there is in Freescale’s “intelligent” sensor line.

Originally, the existence of that microcontroller wasn’t made evident to users, and, even if they knew about it, it wasn’t there for them to program. Its role was to give Freescale a way to take a single sensor and configure it into different products. A classic way of managing different OPNs (ordering part numbers) that can be handled with a single chip.

But, at some point, they opened up the microcontroller, and so this is where the ISF runs. It is particularly intended for systems where there may not be a host and OS; the ISF provides an API and hooks for working with the sensors and other data inputs.

Microcontrollers are increasingly being used as sensor hubs, whether integrated with a sensor or external, both for providing a low-power way of managing sensors without involving the host and as a place to execute sensor and data fusion algorithms. And that’s the ISF’s goal: provide a platform to simplify the creation of systems involving multiple sensors that require some sort of fusion.

If the system also has a host and OS, then a driver would still be needed to access the ISF.

So, details aside, the main point is that the ISF and drivers are separate entities, and you might have one or the other or both. The ISF provides a framework for sensor fusion that’s done below the level of the host. You can find out more in Freescale’s release.

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